Conventionally, a reservation system is known which accepts, on the Internet, reservation of a service such as an accommodation reservation of an accommodation facility and a ticket reservation of a transport facility. In a service that requires reservation, an upper limit of the number of services (for example, the number of guest rooms, the number of seats, and the like) that can be provided in a certain period has been determined. Therefore, the reservation system manages the number of available spots to prevent double booking from occurring.
As a system that accepts reservation of airline ticket, an airline ticket reservation management system is known. As an example of the airline ticket reservation management system, there is a GDS (Global Distribution System) described in Patent Document 1. The airline ticket reservation management system collectively manages the number of vacant seats of each airline company. The airline ticket reservation management system provides airline ticket information, information of the number of vacant seats, and the like to a plurality of travel agents and the like. An information providing apparatus included in each travel agent inquires of the airline ticket reservation management system about a vacant seat status in order to determine whether or not there is a vacant seat in a flight that satisfies conditions specified by a user. At this time, it takes a time of, for example, several seconds to several tens of seconds for a response to the inquiry to be returned from the airline ticket reservation management system. Therefore, the information providing apparatus holds the number of vacant seats which is acquired from the airline ticket reservation management system as a cache and normally provides a vacant seat status to a terminal device based on the held number of vacant seats. For example, when receiving a request of reservation or an inquiry request of vacant seats from a user, the information providing apparatus inquires of the airline ticket reservation management system about the latest vacant seat status.